Strain gauge beams are commonly employed to measure differential pressure. The U.S. Pat. No. 4,791,818 issued on 20 Dec. 1988 discloses a differential pressure transducer with a cantilever beam 30. The sensor of U.S. Pat. No. 4,791,818 comprises a strain gauge beam 46 arranged inside a sensor body 36. An electric sensor 49 such as a piezoelectric ceramic element is affixed to the surface of the strain gauge beam 46. The arrangement employs wires 53, 54 to transmit the electric signal out of the sensor body 36. A measurement of differential pressure in accordance with U.S. Pat. No. 4,791,818 is potentially influenced by the orientation of the cantilever beam sensor 30.
The U.S. Pat. No. 5,844,141 issued on 1 Dec. 1998. U.S. Pat. No. 5,844,141 teaches a sensor 10 with two silicon layers 11a, 11b enclosing a central layer 12. The central layer 12 has two beams 16. The beams 16 of U.S. Pat. No. 5,844,141 form a resonantly vibratable stress-sensitive member. The twin vibratable beams 16 connect via electrically conductive channels 23 to an electric driving signal. The arrangement determines changes in pressure from changes in the resonant frequency of the vibratable beams 16. The resonant frequency of the beams 16 of U.S. Pat. No. 5,844,141 is influenced by ambient factors such as temperature. The sensor of U.S. Pat. No. 5,844,141 thus employs a vibratable fork 20 to compensate for changes in temperature.
The U.S. Pat. No. 7,290,453B2 issued on 6 Nov. 2007. U.S. Pat. No. 7,290,453B2 discloses a pressure sensor assembly with piezo-resistive strain gauges 13 disposed on a force sensing beam. The piezo-resistive strain gauges 13, 14 of U.S. Pat. No. 7,290,453B2 electrically connect to a Wheatstone bridge. The Wheatstone bridge magnifies the conversion of forces into electric signals. The U.S. Pat. No. 7,290,453B2 acknowledges that thin diaphragms exhibit shortcomings. The specification teaches an integral diaphragm-beam and diaphragm-diaphragm approach to obviate problems related to thin diaphragms.